FIG. 16 is a partially exploded perspective view showing a conventional semiconductor device and FIG. 17 is a sectional view showing the same. In FIG. 16, reference numeral 1 designates a multi-layer ceramic plate formed of alumina (Al.sub.2 O.sub.3), reference numeral 2 designates an image sensor chip die bonded to a bottom surface of the multiple-layer ceramic plate 1, reference numeral 3 designates a wire which electrically connects a pad 4 on the chip to an inner lead 5 on the multi-layer ceramic plate 1, reference numeral 6 designates an outer lead electrically connected to said inner lead 5 by a multiple-layer wiring (not shown) in the multiple-layer ceramic plate, reference numeral 7 designates a light shielding plate preventing light from radiating to a part other than the image area 8, and reference numeral 9 designates a glass lid bonded to the multi-layer ceramic plate 1 by a resin.
Operation will be described hereinafter.
Incident light passes through the glass lid 9. Then, only light passing through an opening of the light shielding plate 7 reaches the image area 8 on the image sensor chip 2. Then, a light image is converted to an electric signal by a photo-electric effect. This electric signal is output to the outer lead 6 through the pad 4, the wire 3, the inner lead 5 and the multiple-layer wiring (not shown) of the multi-layer ceramic plate 1 made of alumina.
According to the thus formed conventional semiconductor device, when an image sensor chip made of silicon (coefficient of linear expansion .alpha.=3.04.times.10.sup.-6 {.degree.K .sup.-1 }) is bonded to the multiple-layer ceramic plate made of alumina (coefficient of linear expansion .alpha.=6.8.times.10.sup.-6 {.degree.K .sup.-1 }) using a thermosetting resin at approximately 150.degree. C. and cooled to room temperature (25.degree. C.), the semiconductor device is curved due to the difference between the coefficients of linear expansion of silicon and alumina. A curvature, which is convex when viewed with the silicon chip 2 positioned on the upper side, is generated. FIG. 18 is a graph showing the relation between curvature and the distance from the chip center. As shown in FIG. 18, when the chip has an overall length of 85 mm, a curvature of 200 .mu.m is generated. Therefore, in the conventional semiconductor device, incident light from an optical system does not focus on the image area, so that the semiconductor device does not operate normally internal stress in the chip is high at room temperature, and reliability against heat cycling and the like is low.